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Homework Help: Finding torque in xyz coordinates

  1. Apr 12, 2006 #1
    Problem:
    An engineer estimates that under the most adverse expected weather conditions, the total force on the highway sign in the figure below will be F = 2.48i - 2.88j kN, acting at the center of mass (CM).

    Assume that L1 = 8.13 m and L2 = 6.45 m. What are the x, y, z components of the torque that this force exerts about the base O? Enter components in the order x, y, z.

    i knoe that i have to use the formula T = r X F

    and F = 2.48i - 2.88j + 0k

    i set r = 0i + 8.13j + 6.45k

    and using cross product i got T = 18.576i - 15.996j - 20.1624k N*m

    the answer is still wrong.... what am i doing wrong?
     

    Attached Files:

  2. jcsd
  3. Apr 12, 2006 #2

    dav2008

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    Gold Member

    Without checking any of the work specifically, make sure to account for the fact that the force is given in kiloNewtons, not Newtons.

    As far as your cross product, I think you have a sign reversed.
     
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